This invention relates generally to an apparatus and method for converting a vein for arterial blood flow. More particularly the invention concerns an apparatus and method for expanding a portion of the vein in an area adjacent to an occluded artery, creating an opening through the artery wall and through the expanded portion of the vein wall, creating a fistula between the two openings for blood flow from the artery to the vein, and creating a stationary embolism in the vein proximal to the opening to prevent direct return of the blood to the heart.
The superficial femoral arteries and the popliteal arteries are leg arteries that provide blood flow through the legs and to the feet, particularly to the skin and areas just below the skin. Patients suffering from partial or complete occlusions in such arteries typically experience claudication, i.e., leg pain or limping while walking, and difficulty in healing wounds on the legs due to ischemia, although the deep femoral artery may provide enough circulation that at least the pain is reduced by resting. However, standard open bypass often is impossible on such patients, particularly those with diabetes-narrowed arteries, because of the substandard ability to heal the necessary incisions. Performing angioplasty or inserting stents are unlikely to help where the vessels are too small or the occlusion extends all the way down to the foot. In severe cases, non-healing ulcers or resting pain may leave no alternative except amputation. Thus, peripheral vascular disease presents a serious health risk not adequately addressed by prior means and methods of intervention.
The invented device and method provides for arterializing a peripheral vein lying alongside an artery that is not allowing sufficient blood flow. The complexly branched structure of peripheral veins typically provide more than enough paths for blood flow back to the heart, and thus switching a vein to arterial blood flow may allow sufficient venous blood flow through other veins. The arterialized vein improves arterial blood flow to the fine network of capillaries that the vein formerly drained and, if reconnected, to the artery distal to the occlusion. This results in improved ability to heal wounds and reduced ischemia and claudication. Typically, a vein that is a candidate for arterialization lies roughly parallel and in proximity to the occluded artery, but some distance may separate the vein from the artery in a desired site for creating a fistula proximal to the occlusion.
According to the invention, in a patient having peripheral vascular disease resulting in a partial or total occlusion of a peripheral artery, an angiogram is performed to map the occlusion in the artery and a venogram is performed using a catheter inserted in a parallel, candidate vein from the foot or contra-laterally via the inferior vena cave The venogram catheter is used to inject contrast and thus to map the size and branches of the vein and its proximity to the occluded artery, particularly in an area proximal to the arterial occlusion where the arterial-venous (AV) fistula can be created. The amount of run-off, i.e., venous blood flow, is also assessed to determine the potential downside of arterializing the vein.
Once the vein and the sites for the fistula in the vein and the artery are selected, a venous-expansion catheter that includes a structure for selectively extending outwardly the vein wall is inserted percutaneously into the vein and the structure is maneuvered into position adjacent the venous side of the fistula site. Another catheter is inserted percutaneously into the artery, this catheter including a tool at its distal end capable of creating an opening through the arterial wall and the venous wall. With both catheters in place, the venous-expansion catheter is used to expand the venous wall adjacent the fistula site until the wall touches or at least comes in closer proximity to the arterial wall. Proximity of the walls as well as expansion of the venous wall may also be promoted by attraction between magnetic devices disposed on the catheters. Then, the arterial catheter tool is used to create an opening in the vein and an opening in the artery in close enough proximity that a fistula between the vein and artery can be completed.
The openings may be widened, if necessary, by balloon angioplasty. A stent, or other device for maintaining blood flow through the openings and preventing blood leakage between the vessels, is then inserted through the openings in a compressed state. The stent may include small, radiopaque hooks on each end that embed in the inner walls of the vein and artery. As the stent reverts from a narrowed, lengthened configuration, produced by compression in an insertion device, to its nominal shortened, widened configuration, the hooks pull the vein and artery tightly together, even invaginating the vein into the artery or the artery into the vein. The position of the hooks can be observed radiographically to gauge the connection between the vessels.
Thus, the vein is arterialized, i.e., it receives arterial blood flow in the reverse direction of its previous venous flow. Then, the vein is blocked by depositing a device in the vein proximal to the fistula, either using the original venous-expansion catheter or by a separate thrombus-insertion catheter, in order to promote arterial blood flow to the smaller vessels formerly drained by the vein and to prevent the vein from simply providing a conduit from the fistula back to the heart. Under some circumstances, the vein may be reconnected to the artery distal of the occlusion using a method and apparatus similar to that described above and below for the AV fistula, although such reconnection is often not necessary, and may not be possible in the case of lengthy occlusions. In the case of reconnection of the vein to the artery, a thrombotic device will typically be used to close off the vein distal of the reconnection to the artery. Branches of the vein that lead to areas that are already well-served with arterial circulation, whether or not the vein is reconnected, will be occluded with thrombotic material.
After creation of the fistula and the proximal closing of the vein, an angiogram is performed to assess run-off, and the patient may be helped by the wearing of fill-length support hose to promote run-off. The success of the arterialization is gauged by the patient""s improvement in claudication and ischemia, as well as the increase in the ratio of blood pressure at the ankle to blood pressure at the upper arm, known as ankle-to-brachial index or ABI.
To prevent valves in the arterialized vein from impeding reverse blood flow, a cutting catheter, such as the TECT(trademark) System by InterVentional Technologies, Inc. of San Diego, Calif. or the Rotoblader(trademark) , can be operated in the vein to disable the valves distal to the fistula site. The cutting catheter can be passed into the vein either as part of the venous-expansion catheter or separately through the same route as the venous-expansion catheter before the vein is closed off, or as part of the arterial catheter or along the same route through the fistula.